The inventors of the present application proposed in JP-A-2000-72460 a forming apparatus for bending a glass sheet heated to a temperature close to the softening point in a heating furnace into a glass sheet having a desired curvature. This apparatus conveys a glass sheet heated in the heating furnace, along a conveying plane defined by a plurality of rollers of a roller conveyer, and by moving the rollers up and down according to the position of the glass sheet, a part of the conveying plane is bent with respect to the glass sheet conveying direction and the glass sheet is bent to have a desired curvature.
Meanwhile, U.S. Pat. No. 4,123,246 discloses an apparatus for bending a glass sheet heated to a temperature close to the softening point in a heating furnace, by conveying the glass sheet on a roller conveyer constituted by a plurality of curved rollers each curved with respect to the direction perpendicular to the glass sheet conveying direction.
According to the apparatus disclosed in the above two documents, the softened glass bends down by its own weight along the curved plane, whereby the glass sheet can be bent according to the curved conveying plane.
However, although, JP-A-2000-72460 discloses that a glass sheet is formed to have a plane curved with respect to the glass sheet conveying direction, it does not disclose that a glass sheet is formed to have a plane curved with respect to the direction perpendicular to the glass sheet conveying direction.
Further, the conventional apparatus for bending disclosed in U.S. Pat. No. 4,123,246 had a problem that although it could form a glass sheet to have a curved plane with respect to the direction perpendicular to the glass sheet conveying direction, it could not form a glass sheet to have a curved plane with respect to the glass sheet conveying direction.
Both of these apparatuses have a conveying plane curved only with respect to one direction, and therefore, it is difficult to form a complicatedly curved glass having a plane curved with respect to two directions.
It is an object of the present invention to solve the above problems of the conventional techniques, and to provide a curved roller whose curvature can optionally be changed, and an apparatus for bending a glass sheet, so that a glass sheet having a complicatedly curved shape can be produced.